Toilet bowl cleaners are particularly difficult to design due to the nature of their application and use. An effective cleaner must have sufficient cleaning strength when diluted in the toilet bowl to dissolve and remove scale. In addition, the cleaner must be able to cling to the vertical walls of the bowl. Toilet bowl cleaners may contain mineral acids and have acid values of 140 or more. Unfortunately, these mineral acids can corrode and degrade delicate surfaces and irritate the skin of the user. Toilet bowl cleaners may also contain organic acids and have acid values of 45 or less. However, even though these cleaners create highly acidic conditions, they do not adequately attack scale and require a great deal of time and effort to effectively clean a bowl.
Several patents describe cleaning compositions; however, each of them has several shortcomings. For example, U.S. Pat. No. 5,322,635 to Hieatt is directed to a soap composition. However, this composition does not effectively clean and dissolve scale nor is it able to cling to the vertical walls of the bowl. U.S. Pat. No. 4,269,723 to Barford et al. is directed to a particulate material and solid tablets that slowly dissolve in the cistern of a toilet bowl. This material is a slow acting cleaner and does not facilitate the active scouring of a bowl.
Thus, there is a need in the art for a liquid toilet bowl cleaner that is faster acting, safer and thicker than previous compositions. The cleaner must be a quick and effective means of cleaning a toilet bowl and dissolving lime scale. It must not be corrosive to delicate surfaces or initially irritating to the user. It must also cling to the vertical walls of the bowl and maintain sufficient contact time.